In the manufacture of microelectronic or semiconductor devices, a rapid progress is made toward wafers of larger diameter and reduced thickness. There is a need for the technique capable of encapsulating devices on the wafer level. While the technique for transfer molding solid epoxy resin compositions is conventional, a technique for compression molding liquid epoxy resin compositions is proposed in WO 2009/142065.
The transfer molding technique can cause wire deformation because the resin is flowed into narrow gaps. Short filling is more likely to occur as the encapsulation area becomes larger. The compression molding technique is difficult to precisely control the molding range at an end portion of the wafer. Also, it is not easy to optimize the flow and physical properties of the liquid encapsulating resin when it is fed into the molding machine. With the recent transition of wafers toward larger diameter and reduced thickness, the warpage of the wafer after molding, which is not noticeable in the prior art, becomes a problem. Also better wafer protection is required. It would be desirable to have a wafer molding material which can encapsulate an overall wafer at a time without raising problems including short filling at the wafer surface, and which exhibits minimal warpage and satisfactory wafer protection after molding.
Besides, since encapsulant compositions used with electric/electronic parts are flammable as such, flame retardant agents and additives such as halogen compounds and antimony compounds are added thereto to render them flame retardant. However, from the aspect of reducing the environmental load, the use of these compounds is now limited. Instead, phosphorus based flame retardants are used. The phosphorus based flame retardants, however, can have a negative impact on water quality. There is a need for a molding or encapsulating material free of phosphorus based flame retardant additives.